The role of Core C is to provide mouse models to all research projects. We will pursue two specific aims. Aim 1 includes: 1) coordinating, purchasing and housing immunodeficient (NOD/SCID and NOD/SCID/yc KO) mice, which will be used to prepare humanized mice (see Aim 2) for all projects (except Project 3, as explained in the Research Strategies section);and 2) maintaining and producing immunodeficient porcine cytokine transgenic mice. The porcine cytokine transgenic mice generated in this laboratory provide an excellent murine model for porcine hematopoietic stem/progenitor cell transplantation. These mice will be used to evaluate CD47 gene transduction in porcine hematopoietic progenitors (Project 2), and to prepare hu-mice for assessing human NK cell tolerance to porcine xenografts by mixed hematopoietic chimerism (Project 3). Aim 2 is to provide humanized mouse (hu-mouse) models, including: 1) 'standard'hu-mice with a functional human immune system;2) hu-mice with porcine thymic grafts;3) transgenic hu-mice that express human CD39 transgenes, and 4) porcine chimeric hu-mice with porcine hematopoietic cells expressing a HLA-E/human B2m/peptide trimer. Our approach to generating hu-mice with a functional immune system is to transplant fetal thymus tissue (under renal capsule) and CD34+ hematopoietic stem/progenitor cells (i.v.) in immunodeficient mice. The 'standard'hu-mice will be used to test the immunoregulatory reagents/protocols to be used in non-human primates (Projects 1 and 2). The HLAE/ human p2m/peptide trimer-expressing porcine chimeric hu-mice will be used to assess the potential of NK cell inhibitory ligand expression on porcine cells to induce human NK cell tolerance in Project 3. Hu-mice with porcine thymic grafts and human CD39-overexpresing hu-mice will be used in Project 4 to investigate the role of CD39 in human regulatory T cell development in xenogeneic porcine thymic grafts. The core will prepare and validate the mouse models, and then either perform the proposed experiments (for Projects 1 and 2) or provide 'ready-to-use'models to the investigators (for Projects 3 and 4). As detailed in each research components, these mouse models are essential to the success of this program project.